<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="../react18/react.development.js"></script>
    <script src="../react18/react-dom.development.js"></script>
    <script src="../react18/babel.min.js"></script>
</head>

<body>
    <div id="app"></div>
    <script type="text/babel">
        //用类式组件的方式声明根组件
        class App extends React.Component{
            //构造器中的this指向组件实例
            constructor(){
                super()
                //构造器中的this指向的是组件的实例,这里的handle绑定方法
                this.handle = this.handle.bind(this)
            }

            state = {
                count: 0
            }

            render(){
                console.log(this);
                const {count} = this.state
                return (
                    <div>
                       <button onClick={this.handle}>+</button> 
                       <p>{count}</p>
                    </div>
                )
            }

            handle(){
                alert(1)

                 console.log(this);//undefined,这样就无法
                
            }
        }
        
        const root = ReactDOM.createRoot(document.getElementById('app'))
        root.render(<App/>)



    </script>
</body>

</html>